Loss-of-function mutations such as A104T and M26I in the DJ-1 gene lead to structural destabilization and have been linked to early onset Parkinson's disease. We have recently demonstrated that structural defects in DJ-1 can be corrected by introduction of disulfide bridges that restore WT-like properties in the mutant protein. A pilot screen carried out using differential scanning fluorimetry using a library of 1080 FDA approved compounds yielded a number of molecules that improve the stability of mutant DJ-1. In addition, the same molecules increased the stability of WT DJ-1 as well. Wild type DJ-1 blocks a-synuclein aggregation, a property not shared by the familial mutants. However, the molecules discovered from the screen seem to restore chaperone like function in mutant DJ-1, as well as increase the ability of WT DJ-1 to function as a chaperone for extended periods of time. A structure activity relationship exercise carried out on one of the hits led to the identification of an analog that bound to DJ-1 with a dissociation constant of 480nM. Accurate dissociation constants were determined using isothermal titration calorimetry. The major goal of this proposal is to extend the screening to a larger chemical library to identify diverse classes of molecules for DJ-1, which can work as co-chaperones and block aggregation of a-synuclein. High affinity ligands will represent a starting for development of PD therapeutics, as well as probes for understanding the role of DJ-1 in cell based models in greater details. PUBLIC HEALTH RELEVANCE: Parkinson's disease (PD) is the second most common neurodegenerative disorder. It affects over 1 million Americans and more than 60,000 patients are newly diagnosed each year. Mutation in a recently identified gene product of unknown function, DJ-1, has been implicated in autosomal- recessive early onset PD. The mutations appear to compromise the chaperone like function of DJ-1. The major objective of this proposal is to identify small molecules that would restore normal function in mutants of DJ-1. In addition, these molecules would enhance the function of wild-type DJ-1 and, thereby, have an indirect effect on a greater population of patients with PD and other synucleinopathies.